Fluid pressure relay



Sept. 8, 1931. R. MARSLAND ET AL FLUID PRESSURE RELAY Filed March 24. 1930 2 Sheets-Sheet y HF 0 mm dU mOY Z B O P Sep t. 8, 1931. R. MARSLAND ET AL 1,822,445

FLUID PRESSURE RELA Y Filed Mafch 24, 1930 2 Sheets-Sheet 2 WITNESS INVENTOR F Qolaad Mansland and Q! 0 (gm N. Bryan?- ATTORNEY Patented Sept. 8, 1931 UNITED STATES i v I 1,822,445"

PATENT OFFICE RDLAND MARSLAND, OF MOYLAN, AND OZRON. BRYANT, F MOORES, PENNSYLVANIA, ASSIGNORS TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A

CORPORATION OF PENNSYLVANIA FLUID PRESSURE RELAY Application filed March 24, 1930. Serial No.'438 ,550.

Our invention relates to a fluid pressure relay, and it has for an object to provide a relay of greater sensitiveness.

A further object is to provide a more sensitive relay which is of simple and compact construction.

In a fluid pressure relay required to apply a large force, the hydraulic reaction on the pilot valve effected by the flow of motivating fluid admitted by the pilot valve is relatively great and interferes with the proper positioning of the pilot valve by the comparatively slight variations in the controlling force on the pilot valve.

In accordance with our invention, we provide a second relay to move the pilot valve of the main relay. As the work required of the second relay is very small, it can be made very sensitive.

I11 order to provide a simple and compact construction, the main relay is of the type embodying a tubular pilot valve disposed in a cylindrical bore within the operating piston. In accordance with the present invention, the 25 second relay comprises an operating piston carried by the main pilot valve and disposed in a second cylindrical bore within the main piston and a pilot valve disposed within the interior of the main pilot valve.

The above and other objects are effected by our invention, as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, 1n which:

Fig. 1 is a side elevation of a fluid pressure governor embodying the fluid pressure relay;

Fig. 2 is a sectional view of the relay and,

Fig. 3 shows a modification of a detail.

Referring now to the drawings more 1n detail, we show our novelfluid pressure relay embodied in a fluid pressure governor applied to a steam turbine 11, shown in Fig. 1. The governor 10 includes an 1111- peller 12 mounted on the turbine shaft, and it operates the admission valve in the steam chest 13 through a lever 14 which is fulcrumed at 15. The governor further includes a casing 16 containing the relay and apressure-responsive element, and the fluid pressure developed by the impeller 12 is conveyed to the lower end of the casing 16 through a passage 17.

Referring now to Fig. 2, the relay includes a main operating piston 18 disposed in a cylinder 19 formed by the casing 16. The piston 18 has an upper tubular extension 21,

connected to the lever 14 through a link 22,.

and a lower tubular extension 23, the lower end of which is, at all times, subjected to the fluid pressure developed by the impeller 12. The piston 18, together 'with'its extensions, is formed with a cylindrical bore 24, in whichis disposed a pilot valve 25 which controls the application of fluid pressure to the operating piston.

The cylinder 19 is formed with a discharge opening 26, which communicates with a discharge conduit 27.

The piston 18 is formed with an annular recess 29 in the cylindrical bore. The recess I 29 communicates with the upper end of the cylinder 19 through a plurality of passages 31 formed in the piston. The piston 18 is also formed with an annular row of openings 32, communicating between the cylindrical bore 24 and the lower end of the cylinder 19. The pilot valve 25 is formed, on its outer surface, with an annular recess 33, which, in the normal cut off position of the pilot valve relative to the operating piston, is disposed immediately above the annular recess 29. Immediately below the recess 29, the pilot valve is formed with a second annular recess 34 extending downwardly a sufiicient dis tance to communicate with the openings 32 at all times. The portion between the recesses 33 and 34 constitutes an annular piston portion 30, which normally covers the recess 29 in the piston 18. The piston 24 is further formed with an annular row of openings 35,.communicating between the recess 33 and the interior of the pilot valve.

In order to actuate the pilot valve 25 of the main relay, we provide a second relay comprising a pilot valve 36 and an operating piston 37. The operating piston 37 is carried by the main pilot valve 25 and is disposed in a cylinder 38 formed in the operating piston 18. The pilot valve 36 is disposed within the cylindrical interior of the main pilot valve 25.

The pilot valve is formed with an annular recess 39 on the inner surface thereof, said recess communicating with the upper end of the cylinder 38 through an annular group of openings 41. The pilot valve 25 is also formed with an annular row of open ings 1-2 providing communication between the lower end of the cylinder 38 and the interior of the pilot valve. The lower end of the cylinder 38 communicates with the lower end of the cylinder 19 through openings and the openings 32 in the piston 18.

The pilot valve 36 is formed on its outer surface with an annular recess 43 communieating with the interior thereof through an annular group of openings 44-. It is further formed, on its outer surface, with an annular recess 45, which is in communication, at all times, with the openings 42. The portion between the recesses 43 and constitutes a piston portion l6, which, in normal cut off position of the pilot valve, cuts off communication between the recess 39 and the recess 43 or 45. v

The pilot valve 36 is further formed with arecess e7 which is in communication, at all times, with the openings 35, and which communicates with the interior of the pilot valve through openings 48. The interior of the pilot valve 36 is in connnunication, at all times, with the fluid pressure developed by the impeller 12.

The upper end of the pilot valve 36 is closed, and attached thereto is a spring 49, connected at its lower end to a spring-holding member 51. The impeller pressure biases the pilot valve 36 upwardly in opposition to the force of the spring 49. The deflection of the spring 49 varies with changes in the im peller pressure, and moves the pilot valve 36 to a position corresponding to the value o f impeller pressure.

@The operation of the above-described ap pjiratus is as follows:

Upon a decrease in load on the turbine and nsequent increase in speed, the impeller p i essure is increased and moves the pilot valve 36 upwardly, The recess 39 is placed in communication with the recess 45. As the fliiid in the upper end of the cylinder 38 now escape through the lower end of the cylinder 38 and the passages 40 to the lower end of the cylinder 19, the impeller pressure on the lower end of thepilot valve 25 is elfective to move the pilot valve and the operating piston 37 upwardly. The upward movement of the pilot valve 25 places the recess 29 in communication with the recess 3a,;an-d the fluid in the upper end of the cifilinder 19 is free to flow through the passages 31 and the recesses 29 and 34, to the lower end of the cylinder 19,.permitting the impeller pressure on the lower end of the tubular extension 23 to move the operating piston 18 upwardly. 'Upward movement of the piston 18 effects closing movement of the admission valve 13 to restrict further increase in speed.

Upon an increase in load and decrease in speed, the decreased impeller pressure permits the pilot. valve 36 to be move-d downwardly by the spring 49. The recesses 39 and T3 are placed in communication, admitting impeller pressure to the upper end of the cylinder 38 and moving the piston 37 downwardly. The downward movement of the pilot valve 25 places the recesses 33 and 29 in comn'iunication, admitting fluid pressure to the upper end 'of the cylinder 19 and moving the operating piston 18 downwardly. The downward movement of the operating piston effects opening movement of the admission valve 13 to carry the increased load and to prevent further decrease in speed.

Inasmuch as the area of the operating piston 37 is relatively small, a relatively small amount of flow of fluid is required to effect movement thereof in response to movement of the pilot valve 36. The piston 37, therefore, follows the pilot valve 36 rapidly, and the effect of hydraulic reaction on the piston portion 4. .6 is very small. The hydraulic reaction on the piston portion 30 is readily ovcrcomeby the preponderance of fluid pressure on the operating piston 37 or the lower end of the pilot valve 25, which preponderance of pressure continues until flow into or out of the upper end of the cylinder 38 is cut oil by the piston portion 46. It will be apparent, therefore, that the governor is sensitive to slight variations in pressure and effects an accurate control of the valve 13.

The piste-n portions of the pilot valves, instead of being of uniform width equal to the recesses which they cover, may be lapped for the greater portion of the circumference. This is illust 'ated in Fig. 3 in which the piston portion 30 is wider than the recess 29. It has a plurality of notches 52 in its upper and lower edges, reducing the width of the piston portion at these parts to the width of the recess 29.

Upon a limited movement of the pilot valve 25, which is the usual case, fluid flows only through the notch-cs 52, and the hydraulic reaction is greatly reduced.

Thile we have shown our invention in but one form, it will be obvious'to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and we desire, therefore, that only such limitations shall be placed thereupon as are impose-d by the prior art or as are specificallyset forth in the appended claims.

VVha-t we claim is:

1. In a fluid pressure relay operating in response to a variable fluid pressure, the combination of a main operating piston and a cylinder therefor, a pilot valve controlling the application of fluid pressure to said piston, a piston carried by said pilot valve, a cylinder for the last-mentioned piston, said pilot valve being formed with a cylindrical bore therein, and a second pilot valve within said bore and controlling the application of fluid pressure to the piston carried by the first-mentioned pilot valve, the second pilot valve being subjected to the variable fluid pressure and movable upon variation therein.

2. In a fluid pressure relay, the combination of a main operating piston and a cylinder therefor, said piston being formed with a cylindrical bore therein, a pilot valve disposed in said bore and controlling the application of fluid pressure to said piston, a cylinder formed in said piston, a piston carried by said pilot valve and operating in the lastinentioned cylinder, said pilot valve being formed with a cylindrical bore therein, and a second pilot valve within the last-mentioned bore and controlling the application of fluid pressure to the piston carried by the first- Inentioned pilot valve.

3. In a fluid pressure relay operating in response to a variable fluid pressure, the combination of a main operating piston and a cylinder therefor, said piston being formed with a cylindrical bore therein, a pilot valve disposed in said bore and controlling the application of fluid pressure to said piston, a cylinder formed in said piston, a piston carried by said pilot valve and operating in the last-mentioned cylinder, said pilot valve be ing formed with a cylindrical bore therein, and a second pilot valve Within the last-mentioned bore and controlling the application of fluid pressure to the piston carried by the first-n1entioned pilot valve, the second pilot valve being subjected to the variable fluid pressure and movable upon variation therein.

In testimony whereof, we have hereunto subscribed our names this 19th day of March,

ROLAND MARSLAND. OZRO N. BRYANT. 

